Computer Networks
From the OSI model to what happens when you type a URL.
About Computer Networks
Computer networks are how computers talk to each other, from two laptops on the same Wi-Fi to the whole internet. The subject explains the layers that make this work: physical links, IP addressing and routing, TCP and UDP, and application protocols like HTTP and DNS.
By the end, "what happens when you type a URL into the browser?" becomes a question you can answer step by step.
Why it matters for placements
CN is the second of the three core subjects in fresher interviews. Subnetting numericals and TCP vs UDP are favourites in written tests and technical rounds.
What you'll learn
8 topics · 25 lessons, each with practice
- Explain the OSI and TCP/IP models and what each layer does
- Calculate subnets, network addresses and host ranges
- Compare TCP and UDP, and walk through the three-way handshake
- Explain how DNS, HTTP and HTTPS work
- Answer "what happens when you type a URL" end to end
Foundation Foundation
Take Foundation testRequired. Enough to clear online assessments and service-company interviews.
Basics
Not startedBefore protocols make sense, you need a picture of what is being connected: how big the network is, how the cables are laid out and which box sits in the middle. These words come up in every networking round and in every office setup, so the rest of the course builds on them.
Network Models
Not startedNetworking is too big to reason about in one piece, so it is split into layers that each do one job. Layer models give you a shared vocabulary to say where a protocol lives and where a fault sits. Almost every CN interview starts with a question about them.
Transport Layer
Not startedIP only gets packets to a machine, and it may lose or reorder them on the way. The transport layer delivers data to the right program and, with TCP, makes it reliable. Choosing TCP or UDP and explaining the handshake are standard interview questions.
Application Layer
Not startedThis is the layer you touch as a developer: web requests, domain names and getting an address when you join Wi-Fi. HTTP, DNS and DHCP show up in backend work, debugging and almost every interview that touches the web.
Interview Ready Interview Ready
Take Interview Ready testRecommended. Enough for technical rounds at good product companies.
IP Addressing
Not startedEvery device on a network needs an address, and the way addresses are split decides how networks are sized and routed. Subnetting and CIDR are favourite numerical questions in placement tests, and NAT explains how your home network reaches the internet.
Security Basics
Not startedData crosses networks owned by strangers, so anyone on the path could read or change it. Encryption, TLS and firewalls are the basic tools that keep traffic private and block unwanted access. Every backend developer relies on them, and interviewers expect a clear explanation of how HTTPS stays secure.
Capstone
Not startedReal network traffic uses every layer at once, and seeing them work together is what makes the separate pieces stick. This topic ties DNS, ARP, TCP, TLS and HTTP into one story you can tell in an interview.
Advanced Advanced
Take Advanced testOptional. For top product companies. Never counted against your readiness.
Lower Layers
Not startedBelow IP, frames still have to reach the next device, survive noise on the wire and follow a route across many routers. These layers explain how local delivery, error checking and routing tables actually work. They show up in GATE-style MCQs and in deeper interviews.